Thermally curable wet-impregnated rovings

Abstract

Thermally curable wet-impregnated rovings in which the fibers of the roving are impregnated with liquid polyepoxides lacking polymerizable unsaturation and having dispersed therein a latent heat-activatable epoxy curing catalyst, such as dicyandiamide. The polyepoxide dispersion has a room temperature viscosity of from 2000 to 5000 centipoises and a tack of less than about 6 on a Thwing-Albert inkometer. The rovings are produced without organic solvent using an elevated temperature which is insufficient to activate the curing catalyst and which lowers the viscosity to enable uniform impregnation in the absence of excess impregnant. The wet rovings can be stored without running in a supply package which may be cop wound, and running is also resisted in a void-free wet fiber composite so that the wet composite can be wrapped and then heated to cure the same.

What is claimed is: 
     
       1. Thermally curable wet-impregnated roving in which the fibers of the roving are uniformly impregnated in the substantial absence of excess liquid with a liquid polyepoxide lacking polymerizable unsaturation and having dispersed therein a latent heat-activatable epoxy curing catalyst, said polyepoxide-catalyst dispersion having a room temperature viscosity of from 2000 to 5000 centipoises and a tack of less than about 6 on a Thwing-Albert inkometer. 
     
     
       2. A wet-impregnated roving as recited in claim 1 in which the room temperature viscosity of said polyepoxide dispersion is from 3000 to 4000 centipoises. 
     
     
       3. A wet-impregnated roving as recited in claim 1 in which said polyepoxide dispersion comprises liquid or semi-liquid diglycidyl ethers having an epoxide equivalent weight below about 200. 
     
     
       4. A wet-impregnated roving as recited in claim 3 in which said diglycidyl ethers are diglycidyl ethers of a bisphenol having an epoxide equivalent weight of about 175. 
     
     
       5. A wet-impregnated roving as recited in claim 4 in which said diglycidyl ethers of a bisphenol have mixed therewith from 2% to 20%, based on the total weight of the mixture, of a low viscosity liquid diglycidyl ether of a polyether of a C 2  -C 4  glycol. 
     
     
       6. A wet-impregnated roving as recited in claim 5 in which said low viscosity liquid is a diglycidyl ether of polyoxypropylene glycol having an epoxide equivalent weight of about 190. 
     
     
       7. A wet-impregnated roving as recited in claim 5 in which said epoxy curing catalyst comprises dicyandiamide. 
     
     
       8. A wet-impregnated roving as recited in claim 7 in which said wet-impregnated roving is wound into a supply package in which the wet roving contacts itself longitudinally within the package. 
     
     
       9. The product of claim 8 in which the wet-impregnated roving is twisted before it is wound into the supply package. 
     
     
       10. A wet-impregnated roving as recited in claim 1 in which the fibers in said roving are carbon fibers. 
     
     
       11. Thermally curable wet-impregnated roving wound into a supply package in which the wet roving contacts itself longitudinally within the package, the fibers of said roving being uniformly impregnated in the substantial absence of excess liquid with a dispersion of latent heat-activatable curing catalyst in polyepoxides lacking polymerizable unsaturation, said polyepoxides providing a liquid mixture of liquid or semi-liquid diglycidyl ethers of a bisphenol having an epoxide equivalent weight below about 200 in admixture with from 2% to 20%, based on the total weight of the mixture, of a low viscosity liquid diglycidyl ether of a polyether of a C 2  -C 4  glycol, and dicyandiamide providing said curing catalyst for said diglycidyl ethers, said polyepoxide dispersion having a room temperature viscosity of from 2000 to 5000 centipoises. 
     
     
       12. The product of claim 11 in which said low viscosity liquid is a diglycidyl ether of polyoxypropylene glycol having an epoxide equivalent weight of about 190, and the viscosity of said polyepoxide dispersion is from 3000 to 4000 centipoises.